This revised application for a Mentored Research Scientist Development Award (K01) outlines a 5-year training plan that will prepare the candidate for an independent research career focusing on the study of emotional disorders and their comorbidity. The candidate's career goal is to investigate the latent boundaries that separate the mood and anxiety disorders from one another and from normal emotions and to use this knowledge to enhance the classification and assessment of emotional disturbance. However, while the candidate has a strong background in the anxiety disorders and in Meehl's taxometric method, she requires skills in 4 additional areas to achieve her long-term goals: (1) proficiency in the statistical techniques of classification research beyond the taxometric method;(2) in-depth knowledge of the mood disorders;(3) understanding of variables beyond symptom data (i.e., neurobiological, personality, genetic) that are important for the classification of emotional disorders;and (4) experience with psychiatric epidemiology, the field traditionally enlisted to refine nosological systems. These gaps in knowledge will be addressed by: (1) didactic training in statistics, mood disorders, neurobiology, personality, and genetic epidemiology;(2) clinical training in emotional disorders and their comorbidity;(3) training in psychiatric epidemiology through research apprenticeships on two major surveys designed to inform revisions for ICD-11 and DSM-V;and (4) the conduct of a mentored research project. The research project will integrate the methods of structural and epidemiological research with the aims of (i) delineating the full latent structure of 6 commonly co-occurring mood and anxiety disorders in epidemiological samples, (ii) evaluating the epidemiological consequences of modifying diagnostic criteria and thresholds based on information about latent structure, and (iii) examining epidemiological correlates of pure and comorbid emotional disorders classified using information about their latent structure. This project is expected to inform the development of an R01 proposal to support further research into mood-anxiety comorbidity and to round out the candidate's ability to conduct productive, independent research in this area. The project is also expected to yield results with considerable relevance for public health, with the potential to lead to more valid and useful diagnostic assessments, better detection of individuals in need of services, and more effective prevention and treatment of emotional suffering.